2800cs rear control arms vs 3.0 rear control arms?

[coupe2800cs]

Is there any difference in these with regard to drum brakes and disc brakes, I’m assuming the 2800cs arms don’t have provisions for caliper mounting ?

 

[bmw2800cs]

Rear trailing arm question

Obviously they are easy to tell the diff between 2800CS and 3.0CS w/the brakes still on, but how does one tell with everything removed? e.g.: For example, the ad says 2800CS, but how can one tell...

e9coupe.com

@mulberryworks and @Ohmess :
"

If you are trying to modify a 2800 rear trailing arm to accommodate disk brakes, I don't think that is possible. The 3.0 trailing arms have a machined surface and a set of holes for the installation of the carrier that holds the calipers. That machined surface needs to hold the carrier, and thus the caliper, at precisely the correct orientation relative to the two friction surfaces on the front and rear of the rotor. And the holes need to hold the caliper at the proper angle relative to the outside diameter of the rotor.

You either need 3.0 e9 trailing arms, or go back to drum brakes if you want to keep the 2800 trailing arms.

Well, as has been said before in this thread, anything is possible with enough money, but it would undoubtedly cost more to do it properly (find some disc brake arms to accurately measure the differences, weld on new steel of the right type to your 2800cs arms to make the caliper mount, heat treat the welds to make sure the steel is the proper strength with no built up stresses, machine the new steel to match specs, drill the mounting holes in the right place at the right angle and tap them, repaint or powder coat the arms and install new bearings, install the new calipers and rotors you bought and install arms) than to buy good used 3.0 e9 trailing arms and bolt them on. It's not easy to find disc brake arms, but they do come up from time to time.
"

 

[coupe2800cs]

Appreciate your knowledge on the subject! I’ll have a closer look, but since I have both sets of arms here kinda of deciding what to do with extra stuff like the spare center subframe I have in a effort to make room in my space …

 

[teahead]

3.0 Disc brake arms highly sought after.